Original Paper Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
Received: May 15, 2013 Accepted after revision: October 29, 2013 Published online: January 9, 2014
Split Spinal Cord Malformation: Report of 5 Cases in a Single Chinese Center and Review of the Literature Lifeng Lao Guibin Zhong Xinfeng Li Zude Liu Department of Orthopedic Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
Abstract Background: Split spinal cord malformation (SSCM) is rare in scoliosis. This study evaluated the safety and effectiveness of one-stage surgical treatment of congenital scoliosis (CS) in patients with SSCM in a single Chinese center. Method: A retrospective study of 5 cases who underwent surgery for CS with SSCM (2 type I and 3 type II) from March 2004 to March 2012. Patients included 4 females and 1 male with a mean age of 13.8 years. All patients underwent one-stage posterior fusion surgery with resection of a bony spur firstly in SSCM type I, but we did nothing to the SSCM in type II. Clinical symptoms and radiological changes were evaluated preoperatively and for at least 2 years postoperatively. Results: Preoperatively, 5 patients had variant neurological and other symptoms. They had a mean preoperative Cobb angle of 63 ± 20° and T5–T12 kyphosis of 30 ± 21°. The mean postoperative Cobb angle was 30.2 ± 19.8° with a correction rate of 57.2 ± 17.0%. At the 3-month follow-up the Cobb angle loss was 3.0 ± 6.8°, and at the 2-year follow-up the Cobb angle loss was 6.5 ± 9.7°. Hyperkyphosis was significantly corrected after surgery but correction loss was indicated at the 2-year follow-up (p < 0.01). There were no neurological deficit complications or deteriorated neurological signs postoperative-
© 2014 S. Karger AG, Basel 1016–2291/14/0492–0069$39.50/0 E-Mail [email protected] www.karger.com/pne
ly or at follow-up. Conclusions: One-stage surgical treatment of CS with SSCM could be safe and effective, but we need further multicenter studies with larger samples. Intraspinal intervention of bone spur was recommended in SSCM type I before deformity correction, while in SSCM type II it was needless. © 2014 S. Karger AG, Basel
Introduction
Congenital scoliosis (CS) is the most frequent congenital deformity of the spine [1]. CS is due to anomalous development of the vertebrae during the first 8 weeks of embryological development and is frequently associated with other malformations (spinal cord, heart, kidney) [1]. Diastematomyelia or split spinal cord malformation (SSCM) is a form of spinal dysraphism, referring to a congenital splitting of the spinal cord. It was first reported by Ollivier in 1837 [2]. In the literature, the mortality of SSCM in CS is 4.9–21% [3–5] and the mortality of CS in SSCM is 60–79% [4, 6, 7]. The common view has been that the spur associated with diastematomyelia should be removed prior to any procedure that might cause traction on the spinal cord [7]. As the risk of developing neurological deficits increases with age, all patients should be surgically treated prophylactically even if asymptomatic [8]. Type I and II Zude Liu Department of Orthopedic Surgery, Renji Hospital Shanghai Jiaotong University School of Medicine Shanghai 200127 (China) E-Mail renjispine @ gmail.com
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Key Words Scoliosis · Congenital scoliosis · Split spinal cord malformation · One-stage surgery
Methods Patient Population Between March 2004 and March 2012, 5 CS patients with SSCM (4 females and 1 male) with a mean age of 13.8 years (range 5–18) underwent surgery. All patients underwent one-stage posterior fusion surgery with resection of the bony spur firstly in SSCM type I, but we did nothing to the SSCM in type II. Their preoperative Cobb angle averaged 63 ± 20° (range 34–106°) and mean T5–T12 kyphosis was 30 ± 21° (range 4–74°). This study was approved by the ethics committee of the hospital and informed study consent was obtained from the patients or their guardians. All 5 patients with SSCM included in this study were identified by spinal MRI. Patients were prospectively evaluated for both clinical neurological signs and radiographic changes before and after surgery and at specific postoperative intervals. All 5 patients were followed up for a span ranging from 2 to 7 years (average 3.7). None of the patients had prior spinal surgery before admission. Among the 5 patients, 2 had variant neurological abnormalities, such as limp, paraesthesia, reduced patellar reflex and positive Babinski sign. Other symptoms and signs included back pain, chest distress, endurance decrease, razor back, shoulder imbalance, pelvis imbalance and skin stigmata. Besides, 1 patient was associated with a mild tethered cord. Pre- and postoperative radiographic measurements in the coronal and sagittal plane were made on long-cassette coronal and lateral radiographs of the spine with the patients standing. The thoracic kyphosis angle was measured from the upper endplate of T5 to the lower endplate of T12. Each patient received an examination under MRI and CT to confirm the diagnosis of SSCM. Apical vertebral translation (AVT), apical vertebral rotation (AVR), trunk shift (TS), and Risser sign were also obtained for each examination [8]. All radiographic measurements were done by two of the authors respectively. Surgical Technique Among the 5 patients, 2 underwent posterior instrumentation and fusion, 2 underwent posterior instrumentation and fusion and thoracotomy, and 1 underwent posterior instrumentation and fusion and hemivertebra resection. The surgical procedure was ar-
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Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
ranged in all posterior approaches on the basis of the types of SSCM. In patients with type I SSCM, after intraoperative confirmation of the level of involvement, a midline skin incision was performed and the paravertebral musculature dissected laterally. After exposure of determined levels and placement of instrumentations, a careful laminectomy was performed from the cranial end to the caudal end of the split segment. When the bony spur was exposed, it was dissected extradurally between the two dural sleeves and removed piecemeal by using small bone rongeurs and a sharp osseous chisel. After the dural sleeves were resected, the dural mater was opened and the two dural tubes were rejoined into a whole by suturing the lateral margins of both dural tubes at the midline. We then completed instrumentation and correction of the spinal deformity with a posterior fusion technique. In patients with type II SSCM, we assumed that the spinal cord was a normal one after exposure of determined levels and placement of instrumentations, and thus completed the corrective stage of the surgery, just as in type I SSCM, which was done without any neurosurgical intervention. The overlying musculature, fascia, and skin were closed in anatomical layers (fig. 1). All the patients had either intraoperative wake-up test or somatosensory-evoked potential (SSEP) monitoring. After surgery, the patients were engaged in a supervised physical therapy program and a home exercise protocol to be followed up. Statistical Analysis Statistical analysis was performed with SPSS 14.0 software. Distribution of variables was given as mean, SD, and range. Analysis of variance (ANOVA) was used to make mean comparisons across the groups. Statistical significance was considered with p < 0.05.
Results
During the first week after surgery, there were no neurological deficit complications or deteriorated neurological signs. Intraoperative wake-up tests and SSEP monitoring were all successful. The 2 patients presenting neurological deficits preoperatively had improvement in muscle strength and numbness of the lower limb. At follow-up, neurological symptoms and signs were stable. For the 5 cases, the mean postoperative Cobb angle was 30.2 ± 19.8° with a correction rate of 57.2 ± 17.0%. At the 3-month follow-up, the Cobb angle was 33.2 ± 21.2° and Cobb loss was 3.0 ± 6.8°. At the 2-year follow-up, the Cobb angle was 36.7 ± 21.8° and Cobb loss was 6.5 ± 9.7° (fig. 2). At the 2-year follow-up, AVT was 39.2 ± 38.1 mm, which is significantly different from preoperation and 1-week postoperation (p < 0.05). Compared to preoperation or 1-week postoperation, TS was significantly diminished at the 2-year follow-up (p < 0.01). Hyperkyphosis was significantly corrected after operation and had a correction loss at the 2-year follow-up (p < 0.01) (table 1). Lao/Zhong/Li/Liu
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SSCMs are equally likely to cause neurological deficits and thus should all be surgically explored [9–28]. However, Miller et al. [6] reported that observation of patients with diastematomyelia who had either no deficit or a stable, non-progressing deficit indicated that observation was recommended. Neurosurgery may not improve neurological signs and regrowth of the spur may occur [2]. In addition, neurosurgical complications have remained a problem and two-stage procedures have made correction surgery more difficult [2]. This retrospective study was designed to evaluate the safety and effectiveness of one-stage correction of CS patients with SSCM by firstly removing the bone spur in type I and with a minimum 2-year follow-up at a single Chinese center.
Color version available online
c
a
b
d
Fig. 1. A 15-year-old girl with severe thoracic congenital scoliosis associated with SSCM type I. a Preoperative coronal X-ray (Cobb angle 75°). b Postoperative coronal X-ray (Cobb angle 22°). c Preoperative transverse section of CT scan of SSCM type I. d Spine defor-
mity during operation.
Cobb angle (°)
70
Fig. 2. Trend of Cobb angle following one-
60 50 40 30
stage surgery in CS with SSCM. Cobb angle improved significantly after correction surgery, with Cobb angle loss continuously on follow-up.
Pre-op
Post-op
6 12 Time (months)
18
24
Table 1. Radiologic changes in CS with SSCM (mean ± SD)
Cobb angle, ° AVR AVT, mm TS, mm Normal kyphosis, ° Hyperkyphosis, ° Lumbar lordosis, °
n
Preoperation
Postoperation (1 week)
Postoperation (3 months)
Postoperation (24 months)
5 5 5 5 3 2 5
65.9±23.8 1.8±0.8 59.6±53.1 19.4±19.4 27.1±6.7 59.7±15.0 43.7±17.1
30.2±19.8* 1.7±0.7 29.3±29.2* 16.3±14.8 23.1±13.1 32.1±10.2* 38.1±14.5
33.2±21.2* 1.7±0.8 38.0±34.7* 11.2±12.4*, § 23.5±15.7 35.4±13.9* 37.5±17.2
36.7±21.8*, § 1.7±0.7 39.2±38.1†, § 9.4±11.8*, # 26.3±12.6 40.8±19.8*, # 40.8±19.1
Split Spinal Cord Malformation
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
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* Bonferroni (ANOVA) test (p < 0.01) compared with preoperation. † Bonferroni (ANOVA) test (p < 0.05) compared with preoperation. # Bonferroni (ANOVA) test (p < 0.01) compared with postoperation (1 week). § Bonferroni (ANOVA) test (p < 0.05) compared with postoperation (1 week).
Discussion
CS is due to anomalous development of the vertebrae (failure of formation and/or segmentation) and is frequently associated with other intraspinal malformations [1]. Prahinski et al. [25] reported 9 cases with intraspinal abnormalities after MRI screening of 30 cases of CS. Only 3 of these 9 had plain radiographs and physical examination findings suggestive of their intraspinal abnormalities. Therefore, in order to prevent injury to the spine, we suggest all preoperative CS patients undergo a routine examination via spinal MRI or CT and myelography (CTM). According to Pang et al. [9, 20], SSCM is divided into two types: type I is defined as two hemicords, each within a separate dural tube separated by a dural-sheathed osteocartilaginous medial septum, and type II is defined as two hemicords within a single dural tube separated by a nonrigid fibrous septum. The patients with neurological lesions comprised 40% of those in the current study. This is a much lower incidence than the reported 50–89% neural deficits among patients with diastematomyelia in the literature [3–7, 13]. This may be the result of diagnosing and treating the patients at an early age as we do a routine spine MRI screen of CS in our center. The location of the lesion can occur at any level along the spine but is most frequently seen in the lower thoracic or upper lumbar spine. Most patients present in childhood, with few cases documented in the adult population [11, 17, 18]. Miller et al. [6] reported 63% of SSCMs were located in the lumbar spine. In our study, the locations of the split segments were as follows: in the thoracic segment in 2 cases, in the thoracic-lumbar segment in 2 cases, and in the lumbar segment in 1 case. Erşahin et al. [12] reported that abnormalities associated with split cord malformations are common, and lesions described as capable of tethering the spinal cord have been reported to occur in 85% of patients with SSCM with thickened fila. Mackenzie and Emery [14] reported that the majority of these lesions are discovered in close association with the level of the SSCM and rarely have been reported to occur at 72
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
remote levels of the spinal neuraxis. One patient in our study had tethered cord complications. The literature indicates that SSCM is a sagittal division of a spinal cord or cauda equina segment with a fibrocartilaginous or bone spur that protrudes from the posterior midline portion of one or more vertebral bodies. Traditionally, to avoid creating a neural deficit or increasing a preexisting neural deficit, laminectomy to remove the bone spur has been indicated for patients with diastematomyelia before any procedure for correction of the vertebral column that might cause traction on the spinal cord [3–7, 13, 15]. However, Gan et al. [24] reported that among 17 children (mean age 3.4 years) with diastematomyelia, 14 had excision of spur and cord untethering, and 3 had excision of spur alone. There was improvement of Necker Enfants Malades (NEM) scores postoperatively in only 5 patients, who still had residual deficits. Goldberg et al. [2] reported that 2 cases of SSCM had neurological injury during preventive spur resection and 3 cases had no neurological complications during corrective surgery without previous spur resection. Uzumcugil et al. [16] reported that 18 patients with CS and SSCM underwent spur excision and convex anterior and posterior hemiepiphysiodesis at an average age of 20 months and were followed for a minimum of 2 years. Among these patients, 44% had an epiphysiodesis effect, 44% had a fusion effect, and 12% had a deteriorated deformity. McMaster [3] advised removal of intraspinal anomalies as a prophylactic measure in all children younger than 6 years with CS, regardless of their neural status. Excision of the spur did not result in dramatic improvement in neurological status, but at least none of the patients were made worse. This also was a common finding in the literature reporting on diastematomyelia excision [3, 4, 7, 13]. Miller et al. [6] reported that among 43 patients, resection of the spur was performed in 33 at a mean age of 7 years (range 3 months to 17 years). 22 patients who had a resection had no change in neurological condition, 9 patients had improvement, and 1 patient had one symptom improved and another symptom worsen after the operation. Miller et al. [6] believed that resection of the spur should be performed in patients who had progressive neurological manifestations, while patients without progressive neurological manifestations should be observed; if progression was noted, a resection should then be performed. A review of the literature showed that neural deficit progression was seen predominantly in patients before the age of 5 years [3]. So, should spurs be removed prior to other surgery or not? That is a difficult decision for every surgeon. Lao/Zhong/Li/Liu
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Radiographic examination was very important in preoperative diagnosis and evaluation of neurological signs. In this study, the positive rate in SSCM diagnosis was 100% in MRI. The average number of split segments was 5.6 (SD 3.1) with a range of 2–13. The locations of the split segments were in the thoracic segment in 2 cases, in the thoracic-lumbar segment in 2 cases, and in the lumbar segment in 1 case.
Currently, the criterion of surgery for SSCM is still controversial. A surgical decision in choosing corrective action, with or without neurological intervention, is a key issue, which will be argued with an emphasis on how to choose a prudent strategy for SSCM. Goldberg et al. [2] advised that neurosurgery may not improve neurological signs and regrowth of the spur may occur, in addition, complications due to neurosurgery remained a problem and two-stage procedures made correction surgery more difficult. The risk of neurological deterioration, cerebrospinal fluid leakage, and infection after neurological intervention is about 7–31%, so we must bear in mind that such procedures are not risk-free [21]. Recently, in 2009, Ayvaz et al. [22] reported 32 cases of congenital spinal deformity. There were 18 patients with type I and 14 patients with type II SSCM. While all patients with type I SSCM were managed with neurosurgical intervention (spur excision and dural reconstruction) before corrective surgery, type II SSCM cases were treated by instrumented fusion without neurological intervention. In conclusion, they advised that neurosurgical interventions should be recommended for all type I SSCMs before the corrective surgery to the congenital spinal deformity, whereas patients with type II SSCM can be treated safely without the need of neurosurgical intervention to the SSCM. In 2012, Hui et al. [23] also reported 45 consecutive CS patients with SSCM, and 30 patients were type II SSCM who were treated safely without a need of a neurosurgical intervention. The evaluation of follow-up was very good. In our study, we performed resection of the bone spur before deformity correction and fusion surgery in SSCM type I, and we did nothing to the SSCM in type II. At follow-up the neurological symptoms and signs were stable. However, this result was limited to the small samples in a single center. In this study, the positive rate in SSCM diagnosis was 100% in MRI. In diagnosis of type I SSCM, the positive rate of CTM was 100%. This may be due to the fact that bone spicule was more visible than fiber band on radiography. Erşahin et al. [12] reported the false positive rate of SSCM examination was 17% in MRI, 3% in myelography, and 0% in CTM. Therefore, the priority for a patient suspected of having SSCM should be CTM examination. With the evolution and further accessibility of modern neuroimaging techniques, this condition is becoming more frequently diagnosed [24–28]. Pang et al. [9, 20] recommended that MRI should be performed in patients with myelomeningocele with unusual clinical features, such as inconsistencies between placode and neurological
level and right-left asymmetries. In patients with SSCM below the mid-thoracic level, Pang et al. suggested that because of the high likelihood of finding at least one additional tethering lesion, the entire neuraxis should be imaged. The exact locations of the lesions were not described, and most would be discovered in local radiological examinations of the SSCM [8]. The limitation of this study was obvious. Firstly, it was a retrospective study at a single center and the number of cases was limited. We reported the rare cases and had related literature reviewed in order to acquire a comprehensive understanding of SSCM and discuss the hot point in the future study. Secondly, the average follow-up was 3.7 years and a long-term follow-up is needed for surgical evaluation of the neurological outcome. Thirdly, most CS patients with SSCM came from poor families and could not afford postoperative a MRI examination, which is meaningful for surgical evaluation. In the future, a randomized, prospective and multicenter study is needed for surgical treatment of SSCM.
Split Spinal Cord Malformation
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
Conclusions
All CS patients should undergo MRI or CTM examination to rule out intraspinal anomalies prior to spinal correction surgery. One-stage surgical treatment of CS with SSCM could be safe and effective, but we need further multicenter studies with larger samples. Intraspinal intervention of bone spur was recommended in SSCM type I before deformity correction, while in SSCM type II it was not necessary.
1 Tsou PM, Yau A, Hodgson AR: Embryogenesis and prenatal development of congenital vertebral anomalies and their classification. Clin Orthop 1980;152:211–231. 2 Goldberg C, Fenelon G, Blake NS, Dowling F, Regan BF: Diastematomyelia: a critical review of the natural history and treatment. Spine 1984;9:367–372. 3 McMaster MJ: Occult intraspinal anomalies and congenital scoliosis. J Bone Joint Surg Am 1984;66:588–601. 4 Winter RB, Haven JJ, Moe JH, Lagaard SM: Diastematomyelia and congenital spinal deformities. J Bone Joint Surg Am 1974;56:27–39. 5 Blake N, Lynch A, Dowling E: Spinal cord abnormalities in congenital scoliosis. J Ann Radiol 1986;29:377–379. 6 Miller A, Guille JT, Bowen JR: Evaluation and treatment of diastematomyelia. J Bone Joint Surg Am 1993;75:1308–1317.
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15 McMaster MJ: Congenital scoliosis caused by a unilateral failure of vertebral segmentation with contralateral hemivertebra. Spine 1998; 23:998–1005. 16 Uzumcugil A, Cil A, Yazici M, Acaroglu E, Alanay A, Akalan N, Ozisik P, Surat A: The efficacy of convex hemiepiphysiodesis in patients with iatrogenic posterior element deficiency resulting from diastematomyelia excision. Spine 2003;28:799–803. 17 Kennedy PR: New data on diastematomyelia. J Neurosurg 1979;51:355–361. 18 Dale AJ: Diastematomyelia. Arch Neurol 1969;20:309–317. 19 Bradford DS, Heithoff KB, Cohen M: Intraspinal abnormalities and congenital spine deformities: a radiographic and MRI study. J Pediatr Orthop 1991;11:36–41. 20 Pang D: Split cord malformations. Part II: Clinical syndrome. Neurosurgery 1992; 31: 481–500. 21 Sinha S, Agarwal D, Mahapatra AK: Split cord malformations: an experience of 203 cases. Childs Nerv Syst 2006;22:3–7. 22 Ayvaz M, Akalan N, Yazici M, et al: Is it necessary to operate all split cord malformations before corrective surgery for patients with congenital spinal deformities? Spine 2009;34: 2413–2418.
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23 Hui H, Tao HR, Jiang XF, Fan HB, Yan M, Luo ZJ: Safety and efficacy of one-stage surgical treatment of congenital spinal deformity associated with split spinal cord malformation. Spine 2012;37:2104–2113. 24 Gan YC, Sgouros S, Walsh AR, Hockley AD: Diastematomyelia in children: treatment outcome and natural history of associated syringomyelia. Childs Nerv Syst 2007;23:515–519. 25 Prahinski JR, Polly DW Jr, McHale KA, Ellenbogen RG: Occult intraspinal anomalies in congenital scoliosis. J Pediatr Orthop 2000; 20:59–63. 26 Gupta DK, Mahapatra AK: Proposal for a new clinicoradiological classification of type I split-cord malformations: a prospective study of 25 cases. Pediatr Neurosurg 2006; 42: 341– 346. 27 Sheehan JP, Sheehan JM, Lopes MB, Jane JA Sr: Thoracic diastematomyelia with concurrent intradural epidermoid spinal cord tumor and cervical syrinx in an adult. Case report. J Neurosurg Spine 2002;97:231–234. 28 Börcek AÖ, Ocal O, Emmez H, Zinnuroğlu M, Baykaner MK: Split cord malformation: experience from a tertiary referral center. Pediatr Neurosurg 2012;48:291–298.
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7 Hood RW, Riseborough EJ, Nehme AM, Micheli LJ, Strand RD, Neuhauser EB: Diastematomyelia and structural spine deformities. J Bone Joint Surg Am 1980;62:520–528. 8 Mahapatra AK, Gupta DK: Split cord malformations: a clinical study of 254 patients and a proposal for a new clinical-imaging classification. J Neurosurg 2005;103:531–536. 9 Pang D, Dias MS, Ahab-Bamada M: Split cord malformations. Part I: A unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 1992;31:451–480. 10 Shahcheraghi GH, Hobbi MH: Patterns and progression in congenital scoliosis. J Pediatr Orthop 1999;19:766–775. 11 English WJ, Maltby GL: Diastematomyelia in adults. J Neurosurg 1967;27:260–264. 12 Erşahin Y, Mutluer S, Kocaman S, Demirtaş E: Split spinal cord malformations in children. J Neurosurg 1998;88:57–65. 13 Keim HA, Greene AF: Diastematomyelia and scoliosis. J Bone Joint Surg Am 1973;55:1425– 1435. 14 Mackenzie NG, Emery JL: Deformities of the cervical cord in children with neurospinal dysraphisms. Dev Med Child Neurol 1971;13: 58–67.
Received: May 15, 2013 Accepted after revision: October 29, 2013 Published online: January 9, 2014
Split Spinal Cord Malformation: Report of 5 Cases in a Single Chinese Center and Review of the Literature Lifeng Lao Guibin Zhong Xinfeng Li Zude Liu Department of Orthopedic Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
Abstract Background: Split spinal cord malformation (SSCM) is rare in scoliosis. This study evaluated the safety and effectiveness of one-stage surgical treatment of congenital scoliosis (CS) in patients with SSCM in a single Chinese center. Method: A retrospective study of 5 cases who underwent surgery for CS with SSCM (2 type I and 3 type II) from March 2004 to March 2012. Patients included 4 females and 1 male with a mean age of 13.8 years. All patients underwent one-stage posterior fusion surgery with resection of a bony spur firstly in SSCM type I, but we did nothing to the SSCM in type II. Clinical symptoms and radiological changes were evaluated preoperatively and for at least 2 years postoperatively. Results: Preoperatively, 5 patients had variant neurological and other symptoms. They had a mean preoperative Cobb angle of 63 ± 20° and T5–T12 kyphosis of 30 ± 21°. The mean postoperative Cobb angle was 30.2 ± 19.8° with a correction rate of 57.2 ± 17.0%. At the 3-month follow-up the Cobb angle loss was 3.0 ± 6.8°, and at the 2-year follow-up the Cobb angle loss was 6.5 ± 9.7°. Hyperkyphosis was significantly corrected after surgery but correction loss was indicated at the 2-year follow-up (p < 0.01). There were no neurological deficit complications or deteriorated neurological signs postoperative-
© 2014 S. Karger AG, Basel 1016–2291/14/0492–0069$39.50/0 E-Mail [email protected] www.karger.com/pne
ly or at follow-up. Conclusions: One-stage surgical treatment of CS with SSCM could be safe and effective, but we need further multicenter studies with larger samples. Intraspinal intervention of bone spur was recommended in SSCM type I before deformity correction, while in SSCM type II it was needless. © 2014 S. Karger AG, Basel
Introduction
Congenital scoliosis (CS) is the most frequent congenital deformity of the spine [1]. CS is due to anomalous development of the vertebrae during the first 8 weeks of embryological development and is frequently associated with other malformations (spinal cord, heart, kidney) [1]. Diastematomyelia or split spinal cord malformation (SSCM) is a form of spinal dysraphism, referring to a congenital splitting of the spinal cord. It was first reported by Ollivier in 1837 [2]. In the literature, the mortality of SSCM in CS is 4.9–21% [3–5] and the mortality of CS in SSCM is 60–79% [4, 6, 7]. The common view has been that the spur associated with diastematomyelia should be removed prior to any procedure that might cause traction on the spinal cord [7]. As the risk of developing neurological deficits increases with age, all patients should be surgically treated prophylactically even if asymptomatic [8]. Type I and II Zude Liu Department of Orthopedic Surgery, Renji Hospital Shanghai Jiaotong University School of Medicine Shanghai 200127 (China) E-Mail renjispine @ gmail.com
Downloaded by: University of Tokyo 157.82.153.40 - 5/19/2015 5:01:43 AM
Key Words Scoliosis · Congenital scoliosis · Split spinal cord malformation · One-stage surgery
Methods Patient Population Between March 2004 and March 2012, 5 CS patients with SSCM (4 females and 1 male) with a mean age of 13.8 years (range 5–18) underwent surgery. All patients underwent one-stage posterior fusion surgery with resection of the bony spur firstly in SSCM type I, but we did nothing to the SSCM in type II. Their preoperative Cobb angle averaged 63 ± 20° (range 34–106°) and mean T5–T12 kyphosis was 30 ± 21° (range 4–74°). This study was approved by the ethics committee of the hospital and informed study consent was obtained from the patients or their guardians. All 5 patients with SSCM included in this study were identified by spinal MRI. Patients were prospectively evaluated for both clinical neurological signs and radiographic changes before and after surgery and at specific postoperative intervals. All 5 patients were followed up for a span ranging from 2 to 7 years (average 3.7). None of the patients had prior spinal surgery before admission. Among the 5 patients, 2 had variant neurological abnormalities, such as limp, paraesthesia, reduced patellar reflex and positive Babinski sign. Other symptoms and signs included back pain, chest distress, endurance decrease, razor back, shoulder imbalance, pelvis imbalance and skin stigmata. Besides, 1 patient was associated with a mild tethered cord. Pre- and postoperative radiographic measurements in the coronal and sagittal plane were made on long-cassette coronal and lateral radiographs of the spine with the patients standing. The thoracic kyphosis angle was measured from the upper endplate of T5 to the lower endplate of T12. Each patient received an examination under MRI and CT to confirm the diagnosis of SSCM. Apical vertebral translation (AVT), apical vertebral rotation (AVR), trunk shift (TS), and Risser sign were also obtained for each examination [8]. All radiographic measurements were done by two of the authors respectively. Surgical Technique Among the 5 patients, 2 underwent posterior instrumentation and fusion, 2 underwent posterior instrumentation and fusion and thoracotomy, and 1 underwent posterior instrumentation and fusion and hemivertebra resection. The surgical procedure was ar-
70
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
ranged in all posterior approaches on the basis of the types of SSCM. In patients with type I SSCM, after intraoperative confirmation of the level of involvement, a midline skin incision was performed and the paravertebral musculature dissected laterally. After exposure of determined levels and placement of instrumentations, a careful laminectomy was performed from the cranial end to the caudal end of the split segment. When the bony spur was exposed, it was dissected extradurally between the two dural sleeves and removed piecemeal by using small bone rongeurs and a sharp osseous chisel. After the dural sleeves were resected, the dural mater was opened and the two dural tubes were rejoined into a whole by suturing the lateral margins of both dural tubes at the midline. We then completed instrumentation and correction of the spinal deformity with a posterior fusion technique. In patients with type II SSCM, we assumed that the spinal cord was a normal one after exposure of determined levels and placement of instrumentations, and thus completed the corrective stage of the surgery, just as in type I SSCM, which was done without any neurosurgical intervention. The overlying musculature, fascia, and skin were closed in anatomical layers (fig. 1). All the patients had either intraoperative wake-up test or somatosensory-evoked potential (SSEP) monitoring. After surgery, the patients were engaged in a supervised physical therapy program and a home exercise protocol to be followed up. Statistical Analysis Statistical analysis was performed with SPSS 14.0 software. Distribution of variables was given as mean, SD, and range. Analysis of variance (ANOVA) was used to make mean comparisons across the groups. Statistical significance was considered with p < 0.05.
Results
During the first week after surgery, there were no neurological deficit complications or deteriorated neurological signs. Intraoperative wake-up tests and SSEP monitoring were all successful. The 2 patients presenting neurological deficits preoperatively had improvement in muscle strength and numbness of the lower limb. At follow-up, neurological symptoms and signs were stable. For the 5 cases, the mean postoperative Cobb angle was 30.2 ± 19.8° with a correction rate of 57.2 ± 17.0%. At the 3-month follow-up, the Cobb angle was 33.2 ± 21.2° and Cobb loss was 3.0 ± 6.8°. At the 2-year follow-up, the Cobb angle was 36.7 ± 21.8° and Cobb loss was 6.5 ± 9.7° (fig. 2). At the 2-year follow-up, AVT was 39.2 ± 38.1 mm, which is significantly different from preoperation and 1-week postoperation (p < 0.05). Compared to preoperation or 1-week postoperation, TS was significantly diminished at the 2-year follow-up (p < 0.01). Hyperkyphosis was significantly corrected after operation and had a correction loss at the 2-year follow-up (p < 0.01) (table 1). Lao/Zhong/Li/Liu
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SSCMs are equally likely to cause neurological deficits and thus should all be surgically explored [9–28]. However, Miller et al. [6] reported that observation of patients with diastematomyelia who had either no deficit or a stable, non-progressing deficit indicated that observation was recommended. Neurosurgery may not improve neurological signs and regrowth of the spur may occur [2]. In addition, neurosurgical complications have remained a problem and two-stage procedures have made correction surgery more difficult [2]. This retrospective study was designed to evaluate the safety and effectiveness of one-stage correction of CS patients with SSCM by firstly removing the bone spur in type I and with a minimum 2-year follow-up at a single Chinese center.
Color version available online
c
a
b
d
Fig. 1. A 15-year-old girl with severe thoracic congenital scoliosis associated with SSCM type I. a Preoperative coronal X-ray (Cobb angle 75°). b Postoperative coronal X-ray (Cobb angle 22°). c Preoperative transverse section of CT scan of SSCM type I. d Spine defor-
mity during operation.
Cobb angle (°)
70
Fig. 2. Trend of Cobb angle following one-
60 50 40 30
stage surgery in CS with SSCM. Cobb angle improved significantly after correction surgery, with Cobb angle loss continuously on follow-up.
Pre-op
Post-op
6 12 Time (months)
18
24
Table 1. Radiologic changes in CS with SSCM (mean ± SD)
Cobb angle, ° AVR AVT, mm TS, mm Normal kyphosis, ° Hyperkyphosis, ° Lumbar lordosis, °
n
Preoperation
Postoperation (1 week)
Postoperation (3 months)
Postoperation (24 months)
5 5 5 5 3 2 5
65.9±23.8 1.8±0.8 59.6±53.1 19.4±19.4 27.1±6.7 59.7±15.0 43.7±17.1
30.2±19.8* 1.7±0.7 29.3±29.2* 16.3±14.8 23.1±13.1 32.1±10.2* 38.1±14.5
33.2±21.2* 1.7±0.8 38.0±34.7* 11.2±12.4*, § 23.5±15.7 35.4±13.9* 37.5±17.2
36.7±21.8*, § 1.7±0.7 39.2±38.1†, § 9.4±11.8*, # 26.3±12.6 40.8±19.8*, # 40.8±19.1
Split Spinal Cord Malformation
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
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* Bonferroni (ANOVA) test (p < 0.01) compared with preoperation. † Bonferroni (ANOVA) test (p < 0.05) compared with preoperation. # Bonferroni (ANOVA) test (p < 0.01) compared with postoperation (1 week). § Bonferroni (ANOVA) test (p < 0.05) compared with postoperation (1 week).
Discussion
CS is due to anomalous development of the vertebrae (failure of formation and/or segmentation) and is frequently associated with other intraspinal malformations [1]. Prahinski et al. [25] reported 9 cases with intraspinal abnormalities after MRI screening of 30 cases of CS. Only 3 of these 9 had plain radiographs and physical examination findings suggestive of their intraspinal abnormalities. Therefore, in order to prevent injury to the spine, we suggest all preoperative CS patients undergo a routine examination via spinal MRI or CT and myelography (CTM). According to Pang et al. [9, 20], SSCM is divided into two types: type I is defined as two hemicords, each within a separate dural tube separated by a dural-sheathed osteocartilaginous medial septum, and type II is defined as two hemicords within a single dural tube separated by a nonrigid fibrous septum. The patients with neurological lesions comprised 40% of those in the current study. This is a much lower incidence than the reported 50–89% neural deficits among patients with diastematomyelia in the literature [3–7, 13]. This may be the result of diagnosing and treating the patients at an early age as we do a routine spine MRI screen of CS in our center. The location of the lesion can occur at any level along the spine but is most frequently seen in the lower thoracic or upper lumbar spine. Most patients present in childhood, with few cases documented in the adult population [11, 17, 18]. Miller et al. [6] reported 63% of SSCMs were located in the lumbar spine. In our study, the locations of the split segments were as follows: in the thoracic segment in 2 cases, in the thoracic-lumbar segment in 2 cases, and in the lumbar segment in 1 case. Erşahin et al. [12] reported that abnormalities associated with split cord malformations are common, and lesions described as capable of tethering the spinal cord have been reported to occur in 85% of patients with SSCM with thickened fila. Mackenzie and Emery [14] reported that the majority of these lesions are discovered in close association with the level of the SSCM and rarely have been reported to occur at 72
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
remote levels of the spinal neuraxis. One patient in our study had tethered cord complications. The literature indicates that SSCM is a sagittal division of a spinal cord or cauda equina segment with a fibrocartilaginous or bone spur that protrudes from the posterior midline portion of one or more vertebral bodies. Traditionally, to avoid creating a neural deficit or increasing a preexisting neural deficit, laminectomy to remove the bone spur has been indicated for patients with diastematomyelia before any procedure for correction of the vertebral column that might cause traction on the spinal cord [3–7, 13, 15]. However, Gan et al. [24] reported that among 17 children (mean age 3.4 years) with diastematomyelia, 14 had excision of spur and cord untethering, and 3 had excision of spur alone. There was improvement of Necker Enfants Malades (NEM) scores postoperatively in only 5 patients, who still had residual deficits. Goldberg et al. [2] reported that 2 cases of SSCM had neurological injury during preventive spur resection and 3 cases had no neurological complications during corrective surgery without previous spur resection. Uzumcugil et al. [16] reported that 18 patients with CS and SSCM underwent spur excision and convex anterior and posterior hemiepiphysiodesis at an average age of 20 months and were followed for a minimum of 2 years. Among these patients, 44% had an epiphysiodesis effect, 44% had a fusion effect, and 12% had a deteriorated deformity. McMaster [3] advised removal of intraspinal anomalies as a prophylactic measure in all children younger than 6 years with CS, regardless of their neural status. Excision of the spur did not result in dramatic improvement in neurological status, but at least none of the patients were made worse. This also was a common finding in the literature reporting on diastematomyelia excision [3, 4, 7, 13]. Miller et al. [6] reported that among 43 patients, resection of the spur was performed in 33 at a mean age of 7 years (range 3 months to 17 years). 22 patients who had a resection had no change in neurological condition, 9 patients had improvement, and 1 patient had one symptom improved and another symptom worsen after the operation. Miller et al. [6] believed that resection of the spur should be performed in patients who had progressive neurological manifestations, while patients without progressive neurological manifestations should be observed; if progression was noted, a resection should then be performed. A review of the literature showed that neural deficit progression was seen predominantly in patients before the age of 5 years [3]. So, should spurs be removed prior to other surgery or not? That is a difficult decision for every surgeon. Lao/Zhong/Li/Liu
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Radiographic examination was very important in preoperative diagnosis and evaluation of neurological signs. In this study, the positive rate in SSCM diagnosis was 100% in MRI. The average number of split segments was 5.6 (SD 3.1) with a range of 2–13. The locations of the split segments were in the thoracic segment in 2 cases, in the thoracic-lumbar segment in 2 cases, and in the lumbar segment in 1 case.
Currently, the criterion of surgery for SSCM is still controversial. A surgical decision in choosing corrective action, with or without neurological intervention, is a key issue, which will be argued with an emphasis on how to choose a prudent strategy for SSCM. Goldberg et al. [2] advised that neurosurgery may not improve neurological signs and regrowth of the spur may occur, in addition, complications due to neurosurgery remained a problem and two-stage procedures made correction surgery more difficult. The risk of neurological deterioration, cerebrospinal fluid leakage, and infection after neurological intervention is about 7–31%, so we must bear in mind that such procedures are not risk-free [21]. Recently, in 2009, Ayvaz et al. [22] reported 32 cases of congenital spinal deformity. There were 18 patients with type I and 14 patients with type II SSCM. While all patients with type I SSCM were managed with neurosurgical intervention (spur excision and dural reconstruction) before corrective surgery, type II SSCM cases were treated by instrumented fusion without neurological intervention. In conclusion, they advised that neurosurgical interventions should be recommended for all type I SSCMs before the corrective surgery to the congenital spinal deformity, whereas patients with type II SSCM can be treated safely without the need of neurosurgical intervention to the SSCM. In 2012, Hui et al. [23] also reported 45 consecutive CS patients with SSCM, and 30 patients were type II SSCM who were treated safely without a need of a neurosurgical intervention. The evaluation of follow-up was very good. In our study, we performed resection of the bone spur before deformity correction and fusion surgery in SSCM type I, and we did nothing to the SSCM in type II. At follow-up the neurological symptoms and signs were stable. However, this result was limited to the small samples in a single center. In this study, the positive rate in SSCM diagnosis was 100% in MRI. In diagnosis of type I SSCM, the positive rate of CTM was 100%. This may be due to the fact that bone spicule was more visible than fiber band on radiography. Erşahin et al. [12] reported the false positive rate of SSCM examination was 17% in MRI, 3% in myelography, and 0% in CTM. Therefore, the priority for a patient suspected of having SSCM should be CTM examination. With the evolution and further accessibility of modern neuroimaging techniques, this condition is becoming more frequently diagnosed [24–28]. Pang et al. [9, 20] recommended that MRI should be performed in patients with myelomeningocele with unusual clinical features, such as inconsistencies between placode and neurological
level and right-left asymmetries. In patients with SSCM below the mid-thoracic level, Pang et al. suggested that because of the high likelihood of finding at least one additional tethering lesion, the entire neuraxis should be imaged. The exact locations of the lesions were not described, and most would be discovered in local radiological examinations of the SSCM [8]. The limitation of this study was obvious. Firstly, it was a retrospective study at a single center and the number of cases was limited. We reported the rare cases and had related literature reviewed in order to acquire a comprehensive understanding of SSCM and discuss the hot point in the future study. Secondly, the average follow-up was 3.7 years and a long-term follow-up is needed for surgical evaluation of the neurological outcome. Thirdly, most CS patients with SSCM came from poor families and could not afford postoperative a MRI examination, which is meaningful for surgical evaluation. In the future, a randomized, prospective and multicenter study is needed for surgical treatment of SSCM.
Split Spinal Cord Malformation
Pediatr Neurosurg 2013;49:69–74 DOI: 10.1159/000356890
Conclusions
All CS patients should undergo MRI or CTM examination to rule out intraspinal anomalies prior to spinal correction surgery. One-stage surgical treatment of CS with SSCM could be safe and effective, but we need further multicenter studies with larger samples. Intraspinal intervention of bone spur was recommended in SSCM type I before deformity correction, while in SSCM type II it was not necessary.
1 Tsou PM, Yau A, Hodgson AR: Embryogenesis and prenatal development of congenital vertebral anomalies and their classification. Clin Orthop 1980;152:211–231. 2 Goldberg C, Fenelon G, Blake NS, Dowling F, Regan BF: Diastematomyelia: a critical review of the natural history and treatment. Spine 1984;9:367–372. 3 McMaster MJ: Occult intraspinal anomalies and congenital scoliosis. J Bone Joint Surg Am 1984;66:588–601. 4 Winter RB, Haven JJ, Moe JH, Lagaard SM: Diastematomyelia and congenital spinal deformities. J Bone Joint Surg Am 1974;56:27–39. 5 Blake N, Lynch A, Dowling E: Spinal cord abnormalities in congenital scoliosis. J Ann Radiol 1986;29:377–379. 6 Miller A, Guille JT, Bowen JR: Evaluation and treatment of diastematomyelia. J Bone Joint Surg Am 1993;75:1308–1317.
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